Re: [Xen-devel] [PATCH 0 of 2] pci passthrough: support "managed" pci device in xend for libvirt usage

[Jim Fehlig <jfehlig@xxxxxxxx>]

George Dunlap wrote:
> On Thu, Jan 17, 2013 at 5:29 AM, <cyliu@xxxxxxxx
> <mailto:cyliu@xxxxxxxx>> wrote:
>
>     One of our customers requests parallel pci passthrough
>     functionality between xen
>     (xend and libxl) and kvm, including support managed host pci
>     devices. A
>     "managed" pci device will be made assignable before vm start  and
>     reattach to
>     its original dirver after vm shut off.
>
>     Currently, libvirt supports "managed=yes/no" options in pci device
>     definition.
>     Qemu driver already supports managed pci devices, libxl driver
>     will add that
>     support in libvirt source code. For xend driver, since it's
>     stateful, libvirt
>     can't do much things because libvirt doesn't store much informtion
>     and most
>     work is done by calling xend directly. Even "managed" option won't
>     be stored if
>     xend doesn't support it. For that reason, this patch series tries
>     to add code in
>     xend toolstack to support managed pci devices first, then libvirt
>     can call xend
>     operations directly to support "managed" host pci devices.
>
>     Syntax for managed pci device could be:
>     pci=['0000:00:1a.0,managed=1']
>
>     Please share your comments. Thanks!
>
>
> The first question (before I look at the code closely) is whether we
> want to accept new features into xend.  It's not being actively
> maintained, and we would like to get rid of it at some point.
>
> Given that you seem primarily to be using libvirt, after the 4.3
> release, will there be a strong reason to use xend, instead of just
> using libxl?

Our SLE11 enterprise product uses the legacy toolstack and I doubt we
will change that until SLE12.  We need to give users time to migrate
from the old toolstack as well.

Chunyan first added this functionality to the libvirt libxl driver [1],
since it is preferred going forward.  Unfortunately we need to provide
the same functionality in the old toolstack.  We can carry this patch in
our packages if needed, but upstream backports are certainly preferred
over local patches.

> Note I'm not rejecting it outright; I just think a case needs to be
> made. :-)

Ok, I've made an attempt :).

Regards,
Jim

[1] https://www.redhat.com/archives/libvir-list/2013-January/msg00689.html


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